bims-mideyd 2024-12-22 papers

Int J Mol Sci. 2024 Nov 24. pii: 12619. [Epub ahead of print]25(23):

Blue Light-Induced Mitochondrial Oxidative Damage Underlay Retinal Pigment Epithelial Cell Apoptosis.

Mohamed Abdouh, Yunxi Chen, Alicia Goyeneche, Miguel N Burnier.

Reactive oxygen species (ROS) play a pivotal role in apoptosis. We reported that Blue Light (BL) induced oxidative stress in human retinal pigment epithelial (RPE) cells in vitro and increased drusen deposition and RPE cell apoptosis in human eyes. Here, we investigated the mechanisms underlying BL-induced damage to RPE cells. Cells were exposed to BL with or without the antioxidant N-acetylcysteine. Cells were analyzed for levels of ROS, proliferation, viability, and mitochondria membrane potential (ΔΨM) fluctuation. We performed proteomic analyses to search for differentially expressed proteins. ROS levels increased following RPE cell exposure to BL. While ROS production did not affect RPE cell proliferation, it was accompanied by decreased ΔΨM and increased cell apoptosis due to the caspase cascade activation in a ROS-dependent manner. Proteomic analyses revealed that BL decreased the levels of ROS detoxifying enzymes in exposed cells. We conclude that BL-induced oxidative stress is cytotoxic to RPE cells. These findings bring new insights into the involvement of BL on RPE cell damage and its role in the progression of age-related macular degeneration. The use of antioxidants is an avenue to block or delay BL-mediated RPE cell apoptosis to counteract the disease progression.

Keywords: antioxidant; apoptosis; blue light; caspases activation; mitochondria damage; oxidative stress; retinal pigment epithelial cells

DOI: https://doi.org/10.3390/ijms252312619

FASEB J. 2024 Dec 13. 38(24): e70249

Role of LIPIN 1 in regulating metabolic homeostasis in the retinal pigment epithelium.

Anna S Usoltseva, Christopher Litwin, Michael Lee, Colton Hill, Jiyang Cai, Yan Chen.

Dysregulated lipid metabolism, characterized by the accumulation of lipid deposits on Bruch's membrane and in drusen, is considered a key pathogenic event in age-related macular degeneration (AMD). The imbalance of lipid production, usage, and transport in local tissues, particularly in the retinal pigment epithelium (RPE), is increasingly recognized as crucial in AMD development. However, the molecular mechanisms governing lipid metabolism in the RPE remain elusive. LIPIN1, a multifunctional protein acting as both a modulator of transcription factors and a phosphatidate phosphatase (PAP1), is known to play important regulatory roles in lipid metabolism and related biological functions, such as inflammatory responses. While deficits in LIPIN1 have been linked to multiple diseases, its specific roles in the retina and RPE remain unclear. In this study, we investigated LIPIN1 in RPE integrity and function using a tissue-specific knockout animal model. The clinical and histological examinations revealed age-dependent degeneration in the RPE and the retina, along with impaired lipid metabolism. Bulk RNA sequencing indicated a disturbance in lipid metabolic pathways. Moreover, these animals exhibited inflammatory markers reminiscent of human AMD features, including deposition of IgG and C3d on Bruch's membrane. Collectively, our findings indicate that LIPIN1 is a critical component of the complex regulatory network of lipid homeostasis in the RPE. Disruption of LIPIN1-mediated regulation impaired lipid balance and contributed to AMD-related pathogenic changes.

Keywords: Lipin1; age‐related macular degeneration; lipid; metabolism; retinal pigment epithelium

DOI: https://doi.org/10.1096/fj.202400981R

bioRxiv. 2024 Dec 04. pii: 2024.12.04.626881. [Epub ahead of print]

High resolution imaging and interpretation of three-dimensional RPE sheet structure.

Kevin J Donaldson, Jeffrey H Boatright, John M Nickerson.

The retinal pigment epithelium (RPE) is a monolayer of pigmented cells which plays an essential role in visual function via its interaction with the adjacent neural retina. Typically hexagonal in shape and arranged in a mosaic-like pattern, RPE cells maintain a relatively uniform size and arrangement in healthy eyes. Under stress or disease conditions such as age-related macular degeneration (AMD) and other heritable vision disorders, individual RPE cell dysmorphia has been observed. This has led to investigation of potential cellular compensatory mechanisms which may be dysregulated, affecting proper barrier structure and function. A commonly observed dysmorphic trait is that of enlarged cells which appear to be multinucleated (containing more than two nuclei) when viewed in two-dimensional (2D), immunohistochemically labeled images from the apical surface perspective. One explanation for the multinucleation is that of ongoing cellular fusion which the RPE may be employing to maintain cell-to-cell contact while simultaneously conserving cellular resources in unhealthy tissue. While this may be the most likely interpretation, caution should be applied when interpreting traditional (2D) images which only use cell border outline markers in the absence of lateral markers. Here we present two examples of high-resolution confocal images which allow for three-dimensional (3D) viewing of a traditional apical border delineation marker (ZO-1) and nuclei as well as labeling of alpha catenin which can serve as a lateral cell membrane marker. We find multiple examples in two separate RPE damage models where enlarged, seemingly multinucleate, cells are in actuality not multinucleate and instead appear this way due to surrounding cell nuclei and lateral cell membrane displacement towards the central cell. When viewed from the apical surface, these nuclei appear contained by the ZO-1 border, however when viewed from multiple angles it becomes apparent that this is not the case. This approach calls for more careful analyses in future studies investigating RPE sheet dysmorphia as this could lead to potential misinterpretation of the multinucleation phenomenon and by extension, the potential underlying fusion mechanism.

DOI: https://doi.org/10.1101/2024.12.04.626881

Aging Cell. 2024 Dec 17. e14452

Role of PI3K/AKT/MAOA in glucocorticoid-induced oxidative stress and associated premature senescence of the trabecular meshwork.

Pengyu Zhang, Nan Zhang, Yixin Hu, Xizhi Deng, Min Zhu, Cheng Lai, Wen Zeng, Min Ke.

The oxidative stress-induced premature senescence of trabecular meshwork (TM) represents a pivotal risk factor for the development of glucocorticoid-induced glaucoma (GIG). This study aimed to elucidate the pathogenesis of TM senescence in GIG. MethodsIntraocular pressure (IOP), transmission electron microscopy and senescence-associated protein expression in TM were evaluated in GIG mice. Protein expression of phosphoinositide-3-kinase regulatory subunit 1 (PIK3R1) and monoamine oxidase A (MAOA), phosphorylation of AKT were quantified. ROS and mitochondrial superoxide levels were measured to evaluate cellular oxidative stress. Cell cycle analysis, β-galactosidase staining, senescence-associated protein expression were employed to assess the aging status of primary human trabecular meshwork cells (pHTMs). ResultsmRNA-seq and KEGG analysis indicating PI3K/AKT pathway as a key regulator in TM of GIG. PI3K inhibitor significantly prevented IOP elevation and abnormal mitochondrial morphology of TM in the GIG mouse model. PI3K inhibitor or selective silencing of PIK3R1 alleviated dexamethasone (DEX)-induced oxidative stress, also mitochondrial dysfunction, inhibiting MAOA expression in pHTMs. The same phenomenon was observed in the GIG models with inhibition of MAOA. Further KEGG analysis indicates that cellular senescence is the key factor in the pathogenesis of GIG. TM senescence was observed in both GIG mouse and cell models. Inhibition of the PI3K/AKT/MAOA pathway significantly alleviated DEX-induced premature cellular senescence of TM in GIG models. Glucocorticoids activated the PI3K/AKT/MAOA pathway, leading to mitochondrial dysfunction, oxidative stress, and premature aging in TM, elevating IOP. This mechanism could be associated with the onset and progression of GIG, providing a potential approach for its treatment.

Keywords: PI3K/AKT/MAOA; cell aging; glaucoma; glucocorticoid; mitochondria; oxidative stress; trabecular meshwork

DOI: https://doi.org/10.1111/acel.14452